Breather device for speed-change devices

ABSTRACT

In a breather device linking a space within a transmission case ( 1 ) to outside air, a breather ( 10 ) is provided at a middle position in a lengthwise direction on an upper portion of the transmission case, in particular, at a position displaced in an axial direction from a middle position in the lengthwise direction, and opens to outside air via a ventilating mechanism ( 2 ) that extends in a direction opposite this displaced direction. Thus, through the combination of displacement in a lengthwise direction of the position of the breather with respect to a middle portion in a lengthwise direction of the transmission case and the direction of the ventilating mechanism facing in a direction opposite that direction, the occurrence of breather blow is prevented during both forward and rearward axis tilting of the transmission by an action where a forward side of the ventilating mechanism lowers when,the position of the breather tilts in a direction away from the oil level, and conversely, where the forward side of the ventilating mechanism rises when the position of the breather tilts in a direction towards the oil level.

TECHNICAL FIELD

The present invention relates to a breather device preventing theconfinement of pressure in a space within a transmission case, and inparticular, relates to an art that improves ventilation performance withrespect to an inclination of the transmission mounted in a vehicle.

BACKGROUND ART

Conventionally, a breather device preventing the confinement of pressurewithin a transmission case, particularly in a vertically mountedtransmission for front engine rear drive (FR) vehicles mounted invehicles such as 4WD off-road vehicles, should prevent breather blow,and form a labyrinth structure within the transmission case, in which anexit side of the labyrinth structure is structured to open to outsideair via a breather pipe through a breather plug provided on a frontupper portion of the transmission case, on the assumption that largeforward and rearward tilting occurs in the transmission case when thevehicle is traveling.

In recent years, improvement of the driving performance of 4WD off-roadvehicles such as the above has been demanded, and a breather devicecapable of supporting travel under severe circumstances such as 45°slope roads is becoming necessary.

However, with a conventional breather device such as the above, thepossibility remains that breather blow may be generated by the agitationof oil from a rotating member in an inner portion of the transmissionduring travel on a slope road, particularly travel down a slope road.Fundamentally changing the breather device could be considered as asolution to this breather blow, however, such a large change wouldinvite huge cost increases. In addition, a solution to breather blowwould inevitably be accompanied by an increase in the size of thetransmission exterior such that mountability in a vehicle is worsened.

Hence, it is a primary object of the present invention to provide abreather device for a transmission realizable with minimum alterationsto the conventional transmission case, that prevents breather blowduring vehicle travel on steep slope roads. In addition, it is a furtherobject of the present invention to enable the realization of preventingbreather blow on a steep slope road without increasing the size of thetransmission exterior in practice.

DISCLOSURE OF THE INVENTION

The above objects are achieved by a structure characterized in that abreather device links a space within a transmission case to outside air,in which a breather is provided in an intermediate position in alengthwise direction on an upper portion of the transmission case.

In this structure, oil entering the breather due to excessivefluctuating forward and rearward tilting of the oil level during thetilting of the transmission in both forward and rearward directions, canbe prevented by positioning the breather connected to the breatherdevice at an intermediate portion in the axial direction of an upperportion of the transmission case. Accordingly, the occurrence ofbreather blow caused by oil entering the breather can be preventedduring both forward and rearward tilting of the transmission.

In the above structure, the breather positioned at an intermediateposition in an axial direction of the space within the transmission casedisplaced in a lengthwise direction from a middle position in thelengthwise direction, and opening to outside air via a ventilatingmechanism extending in a direction opposite the direction ofdisplacement is even more effective.

According to this structure, through the combination of displacement ina lengthwise direction of the position of the breather with respect to amiddle portion in a lengthwise direction of the transmission case andthe direction of the ventilating mechanism facing in a directionopposite that direction, the occurrence of breather blow is preventedduring both forward and rearward tilting of the transmission by mutuallysupplementing actions where a forward side of the ventilating mechanismlowers when the position of the breather tilts in a direction away fromthe oil level, and conversely, where the forward side of the ventilatingmechanism rises when the position of the breather tilts in a directiontowards the oil level.

Further, in the above structure, it is possible to employ a structure inwhich the transmission case has a reinforcement rib including a walldemarcating a canal-shaped space in an inner portion extending an upperportion of a peripheral wall in a lengthwise direction and outwardlyoverhanging from the peripheral wall, with the breather opening to thecanal-shaped space provided on a side wall of the reinforcement rib.

In this structure, oil entering the breather due to fluctuations in theoil level can be all the more reliably prevented because it is possibleto set the height of the breather vertically higher than the position ofa general peripheral surface of the transmission case. Moreover, shapechanges of the transmission case are therefore not necessary.

Also, among any of the above structures, a structure in which thebreather is positioned on an outer peripheral side of a non-rotatingmember of the shifting mechanism accommodated within the transmissioncase is also effective.

According to this structure, the non-rotating member of the shiftingmechanism can all the more reliably prevent oil from entering thebreather because it functions as a shielding mechanism of oil raked upby other rotating members.

In addition, among any of the above structures, a structure in which theventilating mechanism is provided with a breather pipe connected to thebreather is also possible.

In this structure, it is possible to structure a breather device thatcan prevent the occurrence of breather blow during both forward andrearward tilting of the transmission without practically changing thetransmission case because the mutually supplementing breather blowpreventive actions can be obtained by rendering the breather pipe, whichis directly fixed to the breather, a ventilating mechanism.

Or, in any of the above structures, a structure in which the ventilatingmechanism is provided integral to the transmission case and isolatedfrom a space within the transmission case, and provided with a breatherchamber linked to the space within the transmission case by the breatheris also possible.

In this structure, the occurrence of breather blow during both forwardand rearward tilting of the transmission can be even more reliablyprevented because the breather chamber functions as a buffer space thathinders oil flow when it enters the ventilating mechanism through thebreather. Also, the breather chamber is integral with the transmissioncase, therefore, the effect of providing the breather chamber can alsobe kept to a minimum.

Or, in any of the above structures, a structure in which the ventilatingmechanism is provided with a breather chamber separate from thetransmission case, and is linked to the space within the transmissioncase by the breather is also possible.

In this structure, the occurrence of breather blow during both forwardand rearward tilting of the transmission can be even more reliablyprevented because the breather chamber functions as a buffer space thathinders oil flow when it enters the ventilating mechanism through thebreather. Also, the breather chamber is separate from the transmissioncase, therefore, substantial changes to the transmission case structurein connection with providing the breather chamber are not necessary.

In addition, in the structure provided with the breather chamber,employing a structure in which the breather chamber is rendered a spacelong in a lengthwise direction, and linked to the space within thetransmission case with an end side thereof by the breather, and anotherend side opens to outside air via the breather pipe is even moreeffective.

In this structure, the occurrence of breather blow during both forwardand rearward tilting of the transmission can be all the more reliablyprevented because the breather chamber is long in a lengthwise directionand functions as a buffer space long in an inclined direction.

In any of the structures provided with the breather chamber, renderingthe breather chamber a labyrinth structure that controls the oil flowwithin the chamber is all the more effective.

In this structure, the occurrence of breather blow can be even moreeffectively prevented because even in the case where oil has entered theventilating mechanism through the breather due to excessively largeforward and rearward tilting of the transmission, oil discharge tooutside air in a ventilating state are inhibited by the labyrinthstructure of the breather chamber.

In addition, the present invention is characterized in that the breatherdevice linking the space within the transmission chamber to outside air,the breather device has a breather that links to a space within the caseat a position offset in a direction from a middle position between afront wall and a rear wall of the transmission case that accommodates ashifting mechanism, and a ventilating mechanism that links to thebreather and extends to a position offset, at the minimum, an identicalamount in another direction from the middle position.

According to this structure as well, through the combination ofoffsetting in one direction from the position of the breather withrespect to the middle position between the front wall and rear wall ofthe transmission case and the offset amount of the ventilating mechanismfacing in a direction opposite that direction, the occurrence ofbreather blow is prevented during both forward and rearward tilting ofthe transmission by mutually supplementing actions where a forward sideof the ventilating mechanism lowers when the position of the breathertilts in a direction away from the oil level, and conversely, where theforward side of the ventilating mechanism rises when the position of thebreather tilts in a direction towards the oil level.

The above structures are particularly effective in the case where thetransmission is a vertical mounted transmission in a vehicle with thecase axis line facing a lengthwise direction of the vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an axial cross-section of a transmission case to which abreather device for a transmission is applied according to a firstembodiment of the present invention;

FIG. 2 is a side view of a section identical to FIG. 1 showing arelation between the breather device and a shifting mechanism accordingto the first embodiment in a partial cross-section;

FIG. 3 is a plane view of the transmission case of the first embodiment;

FIG. 4 is a partial side view of the transmission case of the firstembodiment showing the breather device enlarged;

FIG. 5 is a partial plane view of the transmission case of the firstembodiment showing the breather device enlarged;

FIG. 6 is an enlarged partial side view of a transmission case showing abreather device of a second embodiment;

FIG. 7 is an enlarged partial plane view of the transmission case of thesecond embodiment;

FIG. 8 is an enlarged partial side view of a transmission case showing abreather device of a third embodiment; and

FIG. 9 is an enlarged partial plane view of the transmission case of thethird embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereafter, embodiments of the present invention will be described withreference to the accompanying drawings. FIGS. 1 to 5 are a breatherdevice for a transmission according to a first embodiment of the presentinvention. As shown by the axial cross-section in FIG. 1, the breatherdevice linking a space within a transmission case 1 to outside air isprovided with a breather 10 opening to the space within the case in anintermediate position in an axial direction of an upper portion of thetransmission case 1 connected to a torque converter housing not shown infront in the axial direction (left side in the figure), and an extensionhousing and a transfer for four-wheel-drive similarly not shown at therear (right side in the figure). This breather 10 is positioned in anintermediate position displaced slightly rearward of a middle positionin the axial direction of the space within the case, guides air to anappropriate location of the vehicle via a ventilating mechanism 2extending in a direction opposite this displaced direction, i.e. in aforward direction, and opens to outside air through a vent mechanismsuch as a breather valve not shown.

The space within the case 1 referred to here is a space thataccommodates all rotating members of a shifting mechanism, not shown,and accompanying friction members thereof. It encloses in acircumferential direction with a peripheral wall 11 of the transmissioncase 1, and encloses in a lengthwise direction with a front wall(normally structured with an oil pump fixed to a transmission caseopening portion) 1A separating the transmission case 1 from the torqueconverter housing with an input shaft in a pierced state and a rear wall(normally structured with a rear wall integral to the transmission case1) 1 b separating the transmission case 1 from the extension housing ortransfers for four-wheel-drive with an output shaft in a pierced state.This space is a hermetically sealed oil-tight space in which theshifting mechanism is built because it is an oil lubrication space forthe shifting mechanism, and in practice, is cut off from outside air.Accordingly, an effective lengthwise direction length of the spacewithin the case 1, which is an oil-tight space, is a length in the caseaxial direction with an end set as the front wall, and another end setas the rear wall as shown with a reference numeral L in FIG. 1, and themiddle of this length becomes a middle position in a lengthwisedirection of the space within the case 1.

In this embodiment, the transmission case 1 has a reinforcement rib 12consisting of a wall demarcating a groove-shaped space C in an innerportion, extending to an upper portion of the peripheral wall 11 in alengthwise direction and outwardly overhanging from the peripheral wall11, in which the breather 10 opening to the groove-shaped space C isprovided on a side wall 12 a of the reinforcement rib 12, and aneibow-type breather plug 21 is fixed sidewise to this breather 10.

Furthermore, non-rotating members of the shifting mechanism accommodatedwithin the transmission case 1 such as, for example, a brake piston, anda fixed race of a one-way clutch, which are members supportedunrotatably within the case 1, function as a shielding mechanism in thesense that the direct entry of oil raked up by the rotation of rotatingmembers of the shifting mechanism within the transmission case 1 suchas, for example, each component of a planetary gear, a clutch drum, anda rotation race of a one-way clutch, is prevented, and the abovebreather 10 is provided at a position at an outer peripheral wallthereof. In this embodiment, referring to FIG. 2, the extension tubeportion of a brake piston 42 for an engagement operation with respect toa brake friction member 41, including a plurality of plates, positionedat a generally middle portion in an axial direction with an outerperipheral side secured and supported by an inner peripheral spline 12 sof a peripheral wall of the transmission case 1, extends from ahydraulic servo cylinder 46 built into the rear wall of the case, withan end secured and fitted into by the spline 12 s, and reaching to anend of the brake friction member 41. Therefore, the opening location ofbreather 10 is achieved at an axial position of the outer peripheralside of this extension tube portion. As shown in FIG. 2, the opening ofthe breather 10 is above the brake piston 42, at a location which isaligned with the brake piston 42 in a direction perpendicular to theaxial direction of the case.

As shown in FIGS. 4 and 5, the ventilating mechanism 2 in thisembodiment is provided with the breather plug 21 of the breather 10, anda breather pipe 22 with an end connected to the breather plug 21,another end connected to vehicle-side piping, and thereby ultimatelyconnected to the vent mechanism such as the breather valve via theseconnections. The breather plug 21 is rendered a freely rotatable swiveljoint in a seal weld state around a horizontal axis line of the breather10, and an end side is rendered a seal weldable hose connection shapeinserted into the breather pipe 22. A connecting portion of the breatherplug 21 and the breather pipe 22 is secured by tightening of a hose band23 fitted on an outer periphery of the breather pipe 22. The breatherpipe 22 extends in a generally horizontal forward direction along thereinforcement rib 12, and ends at an outer periphery position of thetorque converter housing connected to the front side of the transmissioncase 1, and a joint 24 for vehicle side piping is fixed to the endportion.

In the breather device having such a structure, when the transmissioncase 1 tilts forward or backward due to the vehicle mounted with thetransmission traveling on a steep slope road, it is possible to preventoil from entering the breather 10 through fluctuations in oil levelduring tilting of the transmission in both forward and rearwarddirections, with the breather 10 connected to the breather devicepositioned at an upper intermediate portion of the transmission case 1.Accordingly, it is also possible to prevent the occurrence of breatherblow due to oil entering the breather 10 during both forward andrearward tilting of the transmission. More specifically, when thetransmission case 1 tilts forward, with the breather 10 at a positiondisplaced rearward a predetermined amount, even if the oil level becomesas high as the front side, oil is prevented from entering the breather10 because the margin of this displaced amount is ensured. On thecontrary, when the transmission case 1 tilts rearward, the margin withrespect to the height of the oil level is only the displaced amount ofthe breather 10 less than that during forward tilting. However, in thiscase, the front side of the breather pipe 22 is higher with respect tothe position of the breather 10, therefore, even if oil were to enterthe breather 10, the occurrence of breather blow can be prevented.

Furthermore, in this embodiment, since the breather 10 is provided onthe side wall 12 a of the reinforcement rib 12 consisting of a walloutwardly overhanging from the highest portion of the general peripheralwall 11 of the transmission case 1, the position of the breather 10 withrespect to the oil level is higher without changing the shape of thetransmission case 1, therefore, the possibility of the breather 10drawing in oil becomes greatly reduced. In addition, there are noprotrusions of the breather plug 21 and the breather pipe 22 from themaximum outer diameter of the transmission case 1 due to the sidewisearrangement of the breather 10 with respect to the side wall 12 a of thereinforcement rib 12, and the mountability of the transmission in thevehicle is unharmed by the employment of this breather device.

Next, FIGS. 6 and 7 show a second embodiment of the present invention.This embodiment differs with respect to the previous first embodiment inthat a breather chamber 3 accompanies a ventilating mechanism 2. Theventilating mechanism 2 in this embodiment is provided integral to thetransmission case and isolated from a transmission case 1 and a spacewithin the transmission case, and provided with the breather chamber 3linked to the space within the transmission case by a breather 10 (seeFIG. 7). The breather chamber 3, as shown with a flat shape in FIG. 7,is rendered a space long in a lengthwise direction and structuredlinking to the space within the transmission case by the breather 10with an end side (rear side in the embodiment) thereof and another endside opens to outside air through a passage identical to the previousembodiment via a breather plug 21 and a breather pipe 22. In otherwords, with respect to the previous embodiment, a structure is used thatdisposes the breather chamber 3 between the breather 10 and the breatherplug 21.

The breather chamber 3 is demarcated using a front portion of thereinforcement rib 12 of the transmission case 1 in the previousembodiment and has a space rendered generally oval from a top view witha height equivalent to a generally protruding amount of thereinforcement rib 12 from the transmission case general peripheralsurface 11, and a width equivalent to the width of the reinforcement rib12. However, it is arranged slightly offset in a left direction in thefigure with respect to a center line of the reinforcement rib 12 due tothe arrangement of the breather pipe 22. A bottom wall 30 of thebreather chamber 3 is formed at a position approximately the same as thegeneral peripheral wall 11 of the transmission case 1 such that it doesnot interfere with the arrangement of the mechanisms within thetransmission case 1, and the breather 10 is formed in a rear portion ofthe bottom wall 30. In addition, an upper portion of thebreather chamber3 is open and rendered a structure that can be closed by screwing of alid 31. Further, the breather plug 21 is fixed to a front of the lid 31by a method identical to the fixing of the breather plug 21 to thebreather 10 in the previous embodiment. The breather chamber 3 isrendered a labyrinth structure that controls the flow of fluid withinthe chamber. In this embodiment, three vertical walls 32 disposedalternately with each other that structure the labyrinth structure areprovided in a connected row arrangement configuration in a thick portionfor screwing of the lid 31. A description of the position of thebreather 10 in a lengthwise direction with respect to the transmissioncase 1, the direction of the breather pipe 22 with respect to this, andfurther piping after the breather plug 21 will be abbreviated becausethey are identical to the case of the previous first embodiment.

According to this embodiment as well, for reasons identical to theprevious first embodiment, it is possible to prevent oil from enteringthe breather 10 due to fluctuations of the oil level during both forwardand rearward tilting of the transmission, thus preventing the occurrenceof breather blow. Furthermore, in the case of this embodiment, thebreather chamber 3 is between the breather 10 and the breather plug 21,functioning as a buffer space that expands the fluid passage area, andfurthermore, that space achieves a mechanism for inhibiting the flow ofoil with the labyrinth structure, therefore, the occurrence of breatherblow is all the more reliably prevented. Also, in this embodiment aswell, since the breather chamber 3 is structured using an inner side ofthe reinforcement rib 12 that outwardly overhangs from the highestportion of the general peripheral wall 11 of the transmission case 1,the effectiveness of preventing breather blow can be all the moreincreased without substantial changes to the shape of the transmissioncase 1. In this case as well, protrusions of the breather chamber 1,breather plug 21, and the breather pipe 22 from the maximum outerdiameter of the transmission case 1 are kept to a minimum, and themountability of the transmission in the vehicle is unharmed by theemployment of this breather device.

Lastly, FIGS. 8 and 9 show a third embodiment of the present invention.This embodiment has a breather chamber 3 as a separate structurecompared to the previous second embodiment. A ventilating mechanism 2 inthis embodiment is provided with the breather chamber 3 separate from atransmission case 1, and linked to a space within the transmission caseby a breather 10 (see FIG. 9). In this case as well, the breatherchamber 3, as shown with a flat shape in FIG. 9, is rendered a spacelong in a lengthwise direction, in which it is linked to a space withinthe transmission case by the breather 10 with an end side (a rear sidein the embodiment) thereof, and another end side (similarly, a frontside) opens to outside air through a passage identical to the previoustwo embodiments via a breather plug 21 and a breather pipe 22.

The breather chamber 3 is provided along a side of a front side portionof a reinforcement rib 12 of the transmission case 1. In the case ofthis embodiment, there are few shape restrictions with it being separatefrom the transmission case 1, therefore, the breather chamber 3 isstructured with a simple box-shaped body 33 in which a rear portion sidewall thereof is a short pipe 34 that links it to a space within thereinforcement rib 12 by a breather 10 formed in a position identical tothe first embodiment. In addition, the breather plug 21 is fixed to afront wall of the body 33, and the breather plug 21 in this case isrendered a ball joint shape to give more space than in the case of theprevious second embodiment to the orientation of the breather pipe 22.Also, in this case as well, the breather chamber 3 has a labyrinthstructure that controls the flow of fluid within the chamber. In thisembodiment, four vertical walls 32 disposed alternately with each otherthat structure the labyrinth structure are respectively formed in shapesthat extend from both side walls of the body 33 nearly to an opposingwall. A description of the position of the breather 10 in a lengthwisedirection with respect to the transmission case 1, the direction of thebreather pipe 22 with respect to this, and the further piping after thebreather plug 21 will be abbreviated because they are identical to thecases of the previous first and second embodiments.

According to this embodiment as well, for reasons identical to theprevious first and second embodiments, it is possible to prevent oilfrom entering the breather 10 due to fluctuations of the oil levelduring both forward and rearward tilting of the transmission, thuspreventing the occurrence of breather blow. Furthermore, in the case ofthis embodiment, similar to the previous second embodiment, the breatherchamber 3 is between the breather 10 and the breather plug 21,functioning as a buffer space that expands the fluid passage area, andfurthermore, that space achieves a mechanism for inhibiting the flow ofoil with the labyrinth structure, therefore, the occurrence of breatherblow is all the more reliably prevented. Also, in this embodiment, thebreather chamber 3 is separate from the transmission case 1, therefore,identical to the case of the first embodiment, practical shape changesto the transmission case 1 are unnecessary. Also, in the case of thisembodiment, the position of the breather 10, identical to the case ofthe first embodiment, is on the side wall of the reinforcement rib 12,and the breather chamber 3 exerts an oil flow inhibiting effectidentical to the case of the second embodiment, therefore, the effect onthe exterior of the transmission case 1 is larger than both the previousembodiments, becoming a breather device having the breather blowprevention effect of the previous two embodiments.

Three embodiments have been described as examples for the sake ofunderstanding the technical idea of the present invention, however, thepresent invention is not limited to the illustrated embodiments, andvarious changes can be implemented to specific structures of it whichare within the scope of the items listed in the individual claims of thescope of the patent claims. In particular, with regard to the positionsetting of the breather 10 with respect to the transmission case 1, ineach of the aforementioned embodiments, its setting was exclusivelyillustrated as displaced in a slightly rearward direction from a middleposition, however, when employing a structure in which the ventilatingmechanism 2 extends in a direction rearward of the transmission case 1,it is clearly preferable for the position of the breather 10 withrespect to the transmission case 1 to be displaced in a somewhat forwarddirection from the middle position, and such a structure is naturallyincluded in the range of the present invention.

INDUSTRIAL APPLICABILITY

The present invention can be widely applied to general transmissions,and more particularly, it is effective for use in automatictransmissions, specifically, in a vertically mounted transmission forfront engine rear drive (FR) vehicles mounted in vehicles such as 4WDoff-road vehicles.

1. A transmission having a case, with a shifting device and a breatherdevice comprising: a breather which links a space within thetransmission case to outside air, wherein the breather opens to a spacewithin the transmission case at an intermediate position in an axialdirection on an upper portion of the transmission case, such that thebreather is displaced in a lengthwise direction from a middle positionin the axial direction of the space within the case, and opens tooutside air via a ventilating mechanism extending in a directionopposite the direction of displacement, a brake friction memberincluding a plurality of plates accommodated within the case; an innerspline extending from a peripheral wall of the case; a hydraulic servocylinder built into a rear wall of the case; and a brake piston with anextension tube portion, accommodated within the case, which is actuatedso that the extension tube portion reaches an end of the brake frictionmember, the extension tube portion being extended from the hydraulicservo cylinder, and an end of the extension tube portion being securedby and fitted into the spline, wherein the breather opens to the spacewithin the transmission case, on an outer side of the extension tubeportion of the brake piston, and at a location which is aligned with theextension tube portion in a direction perpendicular to the axialdirection.
 2. The transmission having a case, with a shifting device anda breather device according to claim 1, wherein the transmission casehas a reinforcement rib comprising a wall on an upper portion of aperipheral wall thereof extending in a lengthwise direction, whichdemarcates a groove-shaped space in an inner portion, outwardlyoverhanging from the peripheral wall, and the breather opening to thegroove-shaped space is provided on a side wall of the reinforcement rib.3. The transmission having a case, with a shifting device and a breatherdevice according to claim 1, wherein the ventilating mechanism isprovided with a breather pipe connected to the breather.
 4. The breatherdevice for a transmission according to claim 1, wherein the ventilatingmechanism is provided integral to the transmission case and isolatedfrom a space within the transmission case, and provided with a breatherchamber linked to the space within the transmission case by thebreather.
 5. The breather device for a transmission according to claim4, wherein the breather chamber is rendered a space long in a lengthwisedirection, and is linked to the space within the transmission case withan end side thereof by the breather, and another end side opens tooutside air via the breather pipe.
 6. The breather device for atransmission according to claim 4, wherein the breather chamber isrendered a labyrinth structure that controls a flow of fluid within thechamber.
 7. The breather device for a transmission according to claim 1,wherein the ventilating mechanism is provided with the breather chamberseparate from the transmission case, and is linked to the space withinthe transmission case by the breather.
 8. A breather device for atransmission according to claim 7, wherein the breather chamber isrendered a space long in a lengthwise direction, and is linked to thespace within the transmission case with an end side thereof by thebreather, and another end side opens to outside air via the breatherpipe.
 9. The breather device for a transmission according to claim 7,wherein the breather chamber is rendered a labyrinth structure thatcontrols a flow of fluid within the chamber.
 10. The transmission havinga case, with a shifting device and a breather device according to claim2, wherein the ventilating mechanism is provided with a breather pipeconnected to the breather.
 11. The breather device for a transmissionaccording to claim 2, wherein the ventilating mechanism is providedintegral to the transmission case and isolated from a space within thetransmission case, and provided with a breather chamber linked to thespace within the transmission case by the breather.
 12. The breatherdevice for a transmission according to claim 11, wherein the breatherchamber is rendered a space long in a lengthwise direction, and islinked to the space within the transmission case with an end sidethereof by the breather, and another end side opens to outside air viathe breather pipe.
 13. The breather device for a transmission accordingto claim 11, wherein the breather chamber is rendered a labyrinthstructure that controls a flow of fluid within the chamber.
 14. Thebreather device for a transmission according to claim 2, wherein theventilating mechanism is provided with the breather chamber separatefrom the transmission case, and is linked to the space within thetransmission case by the breather.
 15. The breather device for atransmission according to claim 14, wherein the breather chamber isrendered a space long in a lengthwise direction, and is linked to thespace within the transmission case with an end side thereof by thebreather, and another end side opens to outside air via the breatherpipe.
 16. The breather device for a transmission according to claim 14,wherein the breather chamber is rendered a labyrinth structure thatcontrols a flow of fluid within the chamber.
 17. The transmission havinga case, with a shifting device and a breather device according to claim1, wherein the intermediate position is a position displaced in thelengthwise direction from the middle position in the axial direction ofthe space within the case.
 18. The transmission having a case, with ashifting device and a breather device according to claim 1, furthercomprising a reinforcement rib that extends along a direction pointingfrom a front to a rear of the transmission case and has a side wall thatfaces in a widthwise direction of the transmission case, the breatherextending from the side wall.